And I'm Audie Cornish. Just when you thought it would be impossible for this program to introduce another series, we're going to squeeze one in. And this one is called Unfolding Science. NPR science correspondent, Joe Palca, wants to tell us about things that fold up and how they unfold in this first installment - the story of a scientific mission that unfolded on Mars.

JOE PALCA, BYLINE: When NASA decided to launch a six-wheeled solar-powered rover to Mars, there wasn't much time to get things ready for the 2003 launch window. So engineers were told, listen up boys and girls. Just use the same landing system you used with the Pathfinder rover in 1998. That rover bounced to the service in a shipping container protected by inflatable airbags. But the new rover, known as Opportunity, was much bigger than Pathfinder. So the question was, could you fit a five-foot-long rover in the same shipping container that a two-foot-long rover fit in.

ROB MANNING: And the answer is you could if you're willing to fold everything up.

PALCA: Rob Manning and his fellow engineers at NASA's Jet Propulsion Laboratory were willing. So they got folding. Anything that stuck out got tucked in. The solar panels -

MANNING: Each solar panel had two folds.

PALCA: The six wheels got folded inward and stored under the rover's body. The five-foot-high mast that held the rover's stereo cameras -

MANNING: Oh, yes. The mast itself had to be stowed sideways across the top deck and hidden inside the folded solar panels.

PALCA: And the robotic arm -

MANNING: Folded right in front tightly knit right against the chest to the rover - also underneath the solar panels.

PALCA: In the end they did it. They squeezed the rover into its tiny shipping container. In fact, they did it twice - squeezing Opportunity's twin rover called Spirit into an equally small container. Now, all that folding saves space but it made for complications. It meant including a lot of actuators and motors and the like - all having to function perfectly and in the right order to accomplish the unfolding. But once on Mars, they all did. First the solar panels unfolded to charge the batteries, then the mast so the camera could have a look around.

MANNING: Altogether it took us about a week to get the rover stood up, wheels locked into position and then to turn and drive off the lander, which was very exciting.